March 17, 2009

A little over a year and some three hundred exo-planet discoveries ago, astronomers at the European Southern Observatory in Chile announced that they had found what might be the first habitable planet outside the solar system. Known as Gliese 581c, the new planet is only five times as massive as the Earth and inhabits a rare sweet zone around a dim red star in the constellation Libra where it is neither too hot nor too cold for liquid water.

Gliese is but a cosmic hop, skip, and jump from Earth -only some 20
light years away (or 120 trillion miles!). Voyager 1, now leaving the
solar system at a speed of about 39,000 miles per hour, would need more
than 300,000 years to travel that far. Or, maybe someday we'll actually
invent a Star Trek-type transporter that reassembles our atoms and
transports us to the farthest reaches of the Cosmos.

For decades, scientists have been debating the conditions that are
needed to replicate an Earth-like probablility of complex beyond the
microbial level. There's not much doubt in the minds of most
astrobiologist that based on extremophile life we've discovered
recently on Earth (see prior posts below), that life on the microbial
level will be discovered sometime in the next twent years on Mars or on
one of Jupiter or Saturn's moons.

The three recent key findings for astrobiology are extremophiles,
extrasolar planets, and a sense that water may be more ubiquitous even
in our own solar neighborhood (in meteors like the Mars' Lafayette,
Europa, and the ice frost on polar Mars). This picture has evolved
quite suddenly with 100-plus extrasolar planets found in just the last
decade (and none known before around 1995).
We now know that the number of planets in our own galaxy could easily
tally in the hundreds of billions. The discovery of Gliese is a visible
clue that a great number of these could be carpeted in the dirty
chemistry we call life. Life on Earth may be unique, but it might not
be miraculous.

Even in the oldest globular cluster star systems in our Milky Way
galaxy -- choked with stars that were born more than 10 billion years
ago -- there's enough "metals" to make earth-like worlds.
According to models of planet formation developed by Dr. Sasselov and
his colleagues of the Geneva discovery team, such a planet should be
about half again as large as the Earth and composed of rock and water,
what the astronomers now call a “super Earth.”

The most exciting part of the find, Dr. Sasselov said, is that it
“basically tells you these kinds of planets are very common.” Because
they could stay geologically active for billions of years, he said he
suspected that such planets could be even more congenial for life than
Earth. Although the new planet is much closer to its star than Earth is
to the Sun, the red dwarf Gliese 581 is only about a hundredth as
luminous as the Sun. "So seven million miles is a comfortable huddling
distance."
But for evolved animal life to be present we need to find that sweet
"Goldilocks" planet with an exceedingly complex host of conditions
present that have given rise the "Rare Earth" hypothesis.

In their book of that title, Rare Earth authors Peter Ward and
Donald Brownlee, both of the University of Washington have outlined a
short list of conditions needed:
Right distance from a star; habitat for complex life; liquid water near
surafce; far enough to avoid tidal lock; right mass of star with long
enough lifetime and not too much ultraviolet; stable planetary orbits;
right planet mass to maintain atmosphere and ocean with a solid molten
core and enough heat for plate tectonics; a Jupiter-like neighbor to
clear out comets and asteroids; plate tectonics to build up land mass,
enhance bio-diversity, and enable a magnetic field; not too much, nor
too little ocean; a large moon at the right distance to stabilize tilt;
a small Mars-like neighbor as possible source to seed Earth-like
planet; maintenance of adequate temperature, composition and pressure
for plants and animals; a aglaxy with enough heavy elements, not too
small, ellipitcal or irregular; right position the galaxy; few giant
impacts like had 65 million years ago; enough carbon for life, but not
enough for runaway greehouse effect; evolution of oxygen and
photosythesis; and, of course, biological evolution.

Dr. Sasselov noted that aliens could have been pointing their antennas
at Earth for 4.6 billion years, without picking up a signal. "Maybe the
inhabitants of Gliese 581c are at the level of the classical Romans . .
. or maybe trilobites." We need to check out hundreds of thousands of
Earthlike worlds.

Comments

Planet Gliese 581c and Planet X/Eris/Nibiru - Planet X is one of many Planets that orbit a dark star or (Brown Dwarf). This Dark Star has five minor planets, the sixth an Earth-sized Homeworld, and the seventh the planet or object we call Nibiru... it is the physical link or "ferry" between our solar system and the dark star system of it's Brown Dwarf Star. Full story:
http://cristiannegureanu.blogspot.com/2009/01/astronomers-discover-earth-like-planet.html

"Why are we stuck on those planets? Are there no new discoveries in the works?"

There's only so much we are able to deduce with our limited technology. Most of the planets we know of are gass giants and those that are not are still several times more massive than our own little rock.

To find planets like Earth, we need to find planets with similar mass and those are just too small to see.. until now that is. ESA has recently launched the Darwin program, which is designed specifically to find these smaller earth-sized planets around distant stars. Once it's up and running, expect a whole new bunch of exciting revelations :)

"ESA's Darwin mission aims to discover extrasolar planets and examine their atmospheres for signs of life, particularly for the presence of certain life-related chemicals such as oxygen and carbon dioxide.

The multi-satellite Darwin mission will use optical interferometry in which at least three separate orbiting telescopes jointly operate as an equivalent single telescope with a much larger effective aperture, thus achieving the required resolution. With this method, multiple smaller telescopes having actual apertures of, for example, 3 metres, can combine to provide an effective aperture of several tens to hundreds of metres, depending on the distance between the individual telescopes."

Gliese 581 c gets 709.17% of the heat, at periastron point in its orbit, that the Earth gets if you use the larger eccentricity suggested, and at least 505.70% if you use the lesser eccentricity. That makes this planet get at least twice the heat that Venus gets. Having 5 times the mass of the Earth means there is a good chance of it having 5 times the greenhouse gas effect. The best estimate makes this planet 10 times hotter than Venus. Don't let anyone fool you into thinking this planet is habitable for anything except rocks.